Guide to UV Measurement
Dichroic Reflectors
Dichroic reflectors are designed to be non-reflective to IR emitted from the lamp. The absorption dichroic reflector absorbs IR at the reflector surface, converting it to heat that is easily removed by cooling air or water. The transmission type of dichroic is usually constructed on a quartz plate, and the IR passes through it to be absorbed by a surface beyond the reflector. Nearly all of the UV is reflected. Whether the transmission-type or absorbing-type, they reduce the focused IR, and consequently the temperature to which the surface rises. Because they reflect UV and not IR, dichroic reflectors of this type are often called cold mirrors since any reflected energy is low in IR.
Some lamp designs also include hot mirrors where the UV is selectively transmitted and the IR reflected. Hot mirrors are positioned between the lamp housing and the work surface.